code: def test_aggregation_description(es):
      feature = AggregationFeature(
          IdentityFeature(es["log"].ww["value"]),
          "sessions",
          Mean,
      )
      description = 'The average of the "value" of all instances of "log" for each "id" in "sessions".'
      assert describe_feature(feature) == description
  
      stacked_agg = AggregationFeature(feature, "customers", Sum)
      stacked_description = (
          'The sum of t{} of all instances of "sessions" for each "id" '
          'in "customers".'.format(description[1:-1])
      )
      assert describe_feature(stacked_agg) == stacked_description
  
file_path: featuretools/featuretools/tests/primitive_tests/test_feature_descriptions.py
imports: import json
  import os
  import pytest
  from woodwork.column_schema import ColumnSchema
  from featuretools import describe_feature
  from featuretools.feature_base import AggregationFeature, DirectFeature, GroupByTransformFeature, IdentityFeature, TransformFeature
  from featuretools.primitives import Absolute, AggregationPrimitive, CumMean, EqualScalar, Mean, Mode, NMostCommon, NumUnique, PercentTrue, Sum, TransformPrimitive
label_desc: Use image node_id 5 for calling a global function with example usage: test_aggregation_description(es) without return types